THE RIGHT SIDE BOLTER OPERATOR, WHILE INSTALLING HIS FIRST ROOF BOLT ON A 20' CUT, BENT THE BOLT THE LAST 14"" AGAINST THE ROOF. WE BELIEVE HE FAILED TO NOTICE HE HAD BENT THE SPINNER WRENCH WH ILE INSTALLING THE BOLT. WHEN HE TRIED TO DRILL A 2ND HOLE WITH THE BENT WRENCH, THE DRILL STEEL WHIPPED AROUND & HIT THE BACK OF HIS HEAD. HE WAS KNOCKED UNCONSCIOUS; TAKEN TO E.R.